DE102004035818A1 - Heat exchanger with latent storage - Google Patents

Abstract

The heat exchanger has a number of pipes (10) for circulation of heat exchange fluid, and heat exchange units (30). A latent storage unit (20) has an effective heat exchange surface, which adjoins to more than 50 percent of the effective heat exchange surface of the pipes. A double wall is provided between the fluid and a latent storage medium. The pipes and/or the storage unit have internal heat conducting and/or structural units.

Description

The The present invention relates to a heat exchanger with latent storage, especially intended for the use in a motor vehicle, e.g. executed in the form of an evaporator with latent storage.

On the field of automotive heating ventilation and / or air conditioning systems come a variety of heat exchangers for use, such as a radiator, which is charged with the drive motor side coolant, or also heat exchangers, the component of a refrigerant circuit are. In the latter case, e.g. regularly Evaporator called heat exchanger used in which a phase transition can take place to air before entering the interior of the vehicle is led to cool. Recently there are also increased heat exchangers without phase transition used, e.g. in so-called CO2 air conditioning systems. regardless The nature and application of such heat exchangers are more common Manner constructed from a variety of plate-shaped elements that are welded in or soldered Condition fluid circulation channels define, wherein between corresponding pairs of such plate structures more common Way heat exchanger fins or - rip are provided, which are hereinafter referred to as heat exchange elements, and which in on and for usual way essentially serve to increase the surface area.

In The last few years have also shown that in specific Applications or situations caching the provided Heat or Cold is desired. For this purpose one uses more usual Way a so-called latent storage device, e.g. the Heat stored in it can be used to preheat the engine, or in the case of Cold storage, around the cold stored in it at short-term shutdown of the vehicle engine, the decommissioning entails the air conditioning bypassing the vehicle interior to be able to air-condition.

An air conditioner having a heat exchanger having a plurality of heat exchange fluid circulation tubes of given effective heat exchange area, and at least one latent storage device having a given effective heat exchange area and provided with heat exchange elements substantially for surface enlargement is shown in FIG EP 1221389 A2 described. The heat exchanger described herein, which corresponds to the preamble of claim 1, should be able to give off, in particular for purposes of reducing the fuel consumption of the vehicle in a so-called idle-stop operation, which was accumulated during normal operation in the latent memory or the latent storage device.

According to an internal state of the art of the Applicant, as in 1 is shown substantially in accordance with the disclosure of EP 1221389 Previous heat exchangers with latent accumulators are based on an intermediate storage of the latent accumulator between a pipe and heat exchange elements provided for the circulation of heat exchanger fluid, wherein heat exchange elements are also formed on the side of the fluid pipes facing away from the latent accumulator device. Up to date, it has been assumed that satisfactory results can be achieved by such an arrangement, both in normal operation, as well as in the case of removal of cold or heat from the latent storage, it has been assumed that the heat transfer from the latent storage to the Heat exchange elements or ribs or fins is decisive, since usually neither circulation nor circulation is provided in the latent memory.

It However, it has been shown that such an arrangement regarding the dynamic response and with respect to evaporator efficiency need of improvement is.

It is accordingly the task the present invention, a heat exchanger of the aforementioned To develop such a way that its dynamic response is improved, preferably with the adaptation also a Improvement in efficiency associated with operation as a refrigerant evaporator should.

The The above object is achieved with a heat exchangers solved, having the features of claim 1, wherein preferred embodiments Subject of the dependent claims are.

In particular, the present invention proposes a heat exchanger, known for example from EP 1221389 A2 with a plurality of tubes provided for heat exchange fluid circulation given heat exchange surface, at least one latent storage device with a given effective heat exchange surface and heat exchange elements, in particular substantially a surface enlargement serving, that the effective heat exchange surface of the latent storage device to more than 50% of effective heat exchange surface of pipes provided for heat exchange fluid circulation borders. In other words, in complete departure from previous practice, the invention proposes that the latent heat storage be substantially surrounded by fluid circulation by covering the effective heat exchange surface with more than 50% of effective heat exchange area of one or more fluids for the tubes. By an effective heat exchange surface is meant that surface of a component which is in heat exchange relationship with another, or an area which is designed for fluid displacement for the purpose of heat exchange. In particular, these are, for example, those surfaces which form the interface between two components or, for example, those which are perpendicular to the directions of circulation.

The Characteristic of the relevant Covering the latent memory with fluid-carrying pipe sections then leads to that an essential part of the latent memory recorded or given heat through fluid circulation volumes before the heat exchange elements, e.g. be achieved in the form of ribs or fins. This However, it is extremely surprising Way not a disadvantage, because the particular application of a latent memory yes, especially in the short-term provision of cold and / or Heat lies, so that at least after brief interruption of the heat fluid circulation the fluid also still exists at the specified target temperature, so that no significant losses are induced here. The heat flow through the fluid circulation tubes when the refrigeration circuit is switched off is further berbessert that the existing in the fluid circulation tubes liquid refrigerant on the warmer side of the slat evaporated and condensed on the storage side and so in the sense a heat pipe in addition Transports heat. At the same time allows this arrangement is an enlargement of the free air passage area between fluid circulation tubes, since an intermediate storage of the latent storage device between the fluid circulation tubes and heat exchange elements only in a reduced degree or also no longer exists, which ultimately the dynamic response clearly to improve, because after resuming the fluid circulation, the fluid directly with the heat exchange elements and is also sufficiently effective area the fluid circulation tubes with respect the heat exchange elements remains.

One much more surprising Advantage that results from the arrangement according to the invention is that Potential wall thicknesses to be able to reduce especially in the area of the interface between latent memory and fluid circulation volume. The inventive arrangement also allows the extensive experience regarding the arrangement of heat exchange elements, e.g. in the form of ribs or fins with respect to the heat exchanger fluid tubes, without having to consider the much more complex temperature transitions that in the case of static latent storage are encountered. Therefore let yourself also the formation of so-called temperature nests in the so-called To avoid idlestop operation effectively, since the heat exchange elements, ie the with air acted upon ribs or fins, however, at least more than 50% with walls of fluid leading Tubes are connected and thus a significant dynamic adaptation enable.

Of further allows the inventive arrangement the use of identical plates to form a heat exchanger, independently whether a latent memory is to be provided or not; on previous heat exchangers with latent storage it was regularly accepted that Only conditionally optimizable temperature transitions are present, if so-called Standard plates has used.

According to one preferred embodiment that for heat exchange fluid circulation provided pipes pipes, each with one of its main surfaces adjoin the latent storage device. Although in principle the inventive concept also in other configurations, e.g. a coaxial arrangement with inside latent memory can be used, it has shown that particularly good results can be achieved, if one for heat exchange fluid circulation provided pipes designed as flat tubes and a latent storage device practically brings sandwich-like between two such flat tubes. The latent memory remote from the sides of the flat tubes are then like in a conventional heat exchangers in engagement with the rib or lamellar heat exchange elements.

According to a preferred embodiment, the tubes provided for the circulation of heat exchanger fluid are flat tubes in which the latent-storage device is arranged, in particular substantially in the center thereof. By an arrangement of the latent memory within a Fluidzirkulationsflachrohres, in particular centrally therein a uniform possible loading and unloading of the latent memory can be ensured. This arrangement also allows the presentation of a higher packing density, especially since the latent storage filling is a non-compressible gel. As part of a Wandungsreduzierung between latent storage medium and thermodynamic fluid could also be a pressurization, providing a corresponding gas cushion or the like, provide, so that both an Optimie tion with respect to the heat transfer between latent storage medium and thermodynamic fluid and vice versa is possible. In this embodiment, it is particularly advantageous that no direct connection must be handled by the latent memory to a heat exchange element, so that this interface in the classic way and in itself only exists between Wärmetauscherfluidflachrohren and ribs or fins.

The inventive arrangement can both regarding of the induced pressure drop when flowing with air as well as with respect to Packing density can be effectively optimized when looking between heat exchange fluid and latent storage medium provides a wall that has a reduced Has material thickness with regard to one in this regard opposing Wall to the heat exchanger fluid circulation provided pipes. This partition wall can thus optimally for a Heat transfer be formed, both in terms of material selection, the thickness as well as the configuration of the intermediate wall itself, because of the Interpretation no further constructive restrictions exist, such as A solderability with Lamellae.

The Wall between heat exchanger fluid and Latent storage medium can also be designed as a double wall, which is formed from substantially plane-parallel sheets. By providing a double wall, the latent storage device separately manufactured and filled are then arranged in accordance with between two plate elements to be, which form on both sides of Latentspeichereinreichung fluid circulation channels can. Plan parallel plates also allow intimate contact with minimal losses during the passage of temperature, occurring during loading or Discharge the latent memory.

According to one preferred embodiment internally provided for heat exchanger fluid circulation Tubes and / or internally of the latent storage device or devices internal heat-conducting elements and / or inner structural elements formed. The provision of inner Structures Reposes the latent memory improved loading and unloading characteristics ready. heat-conducting elements in the volumes provided for fluid circulation also allows if there is no circulation, satisfactory heat conduction from the latent storage to the fins or fins of the heat exchanger. The heat-conducting elements yourself can also serve as structural elements or structural elements can also additionally be educated. By providing structural elements is a further material thickness reduction possible because e.g. by using so-called inserts on the one hand a more even pressure distribution guaranteed can be, as well as on the other hand, a stiffening of surfaces, the be pressurized. The Wärmeleit- and / or structural elements can further, as far as disposed in the fluid circulation volumes, also Provide fluid deflecting means or partitions, e.g. around a U-shaped circulation to effect.

advantageously, The latent storage device extends substantially over the entire height the heat exchanger, in particular with the formation of a widening, in particular on the Level of a collector leading to heat exchanger fluid circulation provided pipes. In other words, it is preferable that contrary to previous arrangements of the latent memory over the with Slats or ribbed portion of the heat exchanger extends, for additional volume for latent storage medium to be able to provide. This design should be natural guarantee, that corresponding passages are provided in the latent storage elements to control the fluid circulation, e.g. at the level of the collector housing not to be affected.

alternative or in addition to the extent of the latent storage device can be provided that the latent storage device over the entire range of for heat exchange fluid circulation provided pipes only about extends a part of the heat exchanger depth, especially about the upstream side Part of it. Such an embodiment can on the one hand at a Part of the heat exchanger depth, e.g. the downstream side Area a big one flow volume provide also the outflow characteristics through the whole Reduction in the extension of the slats not provided Passage sections can be reduced, so that the pressure loss and the tendency to get carried away from condensation droplets reduced.

Around compared to a heat exchanger without being able to reduce latent storage induced pressure drops is it is further preferred that the heat exchange fluid circulation provided tubes and / or the latent storage device upstream of the heat exchanger rejuvenating and / or rounded are formed. A tapered configuration with supplementary or alternatively rounded leading edges may lead to another Reduction of air flow impairment to lead, additionally to the already existing optimization possibility with regard to the to be used material thicknesses for the walls in the transition area between latent storage medium and thermodynamic fluid.

Particularly advantageous effect of the inventive concept in applications, in where the heat exchanger is designed as an evaporator, in particular as an evaporator, which is operated with a heat exchange fluid with phase transition temperatures of about 6 ° C, although corresponding benefits can be achieved in another heat exchanger, such as a heat exchanger, cached in the heat for engine preheating or other applications can be.

Essential for the Invention is ultimately in the comparison between a heat exchanger without Latent storage and a heat exchanger with latent memory, that more usual This results in power losses of about 10% and a 60% higher pressure drop result, whereby the concept according to the invention makes it possible to To counteract these disadvantages clearly. In operation draws a heat exchanger according to the invention through outstanding and discharge characteristics of the latent memory and by an improved Responsiveness when starting the fluid circulation off, as well by consistently high performance, eg. B. in operation as an evaporator because the elimination of heat immersion elements by enlarging the inner heat transfer surface between the heat exchange fluid and the inner tube surface is compensated.

Further Advantages and features of the present invention are further apparent clearly reading the following by way of example only Description of some currently preferred embodiments. The description is to be considered as non-limiting, but given for the purpose of illustration only, with reference to the attached Drawings in which:

1 shows a heat exchanger with latent storage device according to an internal prior art.

2 schematically shows a control algorithm for a heat exchanger according to the invention, which is designed as an evaporator of a vehicle air conditioning system.

3 shows a schematic sectional view of a first preferred embodiment of a heat exchanger according to the invention, wherein for brevity two variants are shown.

4 shows a detail view in accordance with a further variant.

5 shows a detailed view with respect to the lower end portion of a heat exchanger according to the invention, again showing two different variants.

6 shows a detail of a further heat exchanger as an embodiment of the present invention according to a further alternative.

7 shows in a detail view one of in 5 variants shown, but without displacement of the latent memory beyond the range of the heat exchange elements addition.

8th shows schematically a plate which is suitable for constructing a heat exchanger according to the invention, again representing two alternatives.

1 shows a schematic sectional view of a section with respect to a heat exchanger with latent memory according to an internal state of the art of the applicant, in construction comparable to the heat exchanger, as described in the EP 1221389 A2 , The heat exchanger comprises flat tubes, as they are at the reference numeral 10 are given, from the usual structure, ie formed by two correspondingly shaped plates which form between them the fluid circulation space. In the drawing right seen with respect to the flat tube 10 are common for heat exchangers heat exchange elements in the form of fins or ribs 30 provided, which serve essentially for surface enlargement on the air side. On the left side of the illustration of 1 of the flat tube 10 is each a latent storage device 20 educated. On the side facing away from the flat tube of the latent memory are in turn heat exchange elements 30 arranged. In operation circulates accordingly in the flat tubes 10 the heat exchange fluid, wherein in the case of using an evaporator cooling power is provided, which is discharged directly to the fins on the right side and used on the left side to charge the memory, after which this cold after passing through the latent memory to the fins 30 can be passed on.

As can be clearly seen, the provision of the latent storage devices entails a reduction of the passage area for air flow through the heat exchange elements, resulting in considerable pressure losses, in particular also due to the use of the different wall materials. The heat transfer between flat tube 10 and latent memory 20 takes place only partially satisfactory and it has been found, in particular, that in incomplete loading of the latent memory can build up in this a Temperaturgadient, both seen from left to right and in height, being said in the latter case of so-called temperature nests , The behavior described above results mainly from the usual way static filling of the latent storage device.

If one considers the case, which is also called Idlestop in the vehicle sector, then the latent memory previously loaded only over one area will be considered 20 Heat up or release, for example, in the case of an evaporator application, the latent storage on the left side can give off cold directly on fins or ribs, while on the right side cold to the now no longer circulating fluid in the flat tube 10 will give, after which this cooling power is in turn delivered to the right lying the arrangement flat tube latent storage located fins or ribs. In particular, in the case where the latent memory is not completely loaded as described above, this results in insufficient cooling performance which has been attempted to counteract making the latent memory even bulkier, but hardly in terms of air flow dynamics is feasible, especially in view of the low space available in automotive applications.

When restarting the vehicle, respectively when restarting the circulation of the fluid in the flat tubes 10 In turn, a portion of the thermal power on the right side is delivered directly to the heat exchange elements, while a part must pass through the latent heat storage before he the corresponding left-sided fins 30 can reach. It has now been recognized, however, that the response in this situation may be unsatisfactory, especially since, after interruption of the fluid circulation, it is often desirable to be able to provide maximum thermal performance for the passing air.

In Considering the above statements to the prior art suggests the invention in complete departure from the prior art, at the flat tubes and the latent memory provided side by side are, in front, the common area increase between latent storage and fluid circulation volume and the indirect heat conduction path from reducing fluid circulation volume to the heat exchange elements, without additional To require space.

3 shows a preferred embodiment of a heat exchanger according to the invention in a schematic sectional view, similar to the representation of 1 , where in principle two alternatives for tighter representation in one and the same drawing are shown. As above, fluid circulation tubes 10 , Latent storage elements 20 and heat exchange elements 30 provided, however, the latent storage device 20 sandwiched by two fluid circulation volumes. On the one hand, this representation can be achieved by designing two separate volumes for fluid circulation on the right and left of the latent memory, wherein, alternatively, integration of the latent accumulator into a flat tube volume thus formed is possible. In the embodiment illustrated concretely who the fluid circulation volumes, for example, formed by that to the latent memory 20 Standard evaporator plates with structural elements 16 be attached. Alternatively, as shown at the reference numeral 14 It is also possible to define the circulation volume by means of a substantially flat plate with respect to the latent storage device and additionally therein, a Wärmeleit- and / or -strukturseinrichtung 14 for example, as shown in the form of stacked zig-zag inserts.

In 4 another alternative is shown. The structure is in principle comparable to that in 3 shown, but in each case a rectangular shaped heat conduction and support structure is introduced in the fluid circulation volumes, while also the latent storage device 20 with a corresponding heat-conducting and / or structure-increasing device 22 equipped, in the present case a simple Wärmeleitblech. The lamellar structure thus formed is provided at a pitch of 0.5 to 1 mm. It should be noted that, due to the structural characteristics of such an insert, it is possible to reduce the wall thickness from the usual 0.52 mm to 0.25 mm to 0.35 mm without changing the pressure resistance.

A heat exchanger according to the invention can, for example, serve as an evaporator with the following, for example, in US Pat 2 be operated algorithm to ensure in each state that the evaporation temperature is at least 1 to 2 K below the solidus temperature of the phase change material. The adjustment of the cooling capacity, starting from a setting for maximum power can be carried out such that in a first step, the air mass flow is reduced to the minimum value for comfort control, eg from about 450 to 750 kg / h to a minimum air mass flow of 180 to 320 kg / h , Following this, one can increase the pleasure outlet temperature while maintaining the minimum comfort air flow rate constant until the evaporator temperature reaches the phase transition temperature geade. By within the fluid circulation 10 located latent handler device 20 For example, it is possible to achieve a conventional heat exchange effect of 70% air outlet temperatures, which are 4 to 6 K above the liquidus temperature of the latent storage material. Following this, a reheating of the air or reheating of the air can be provided.

The configuration according to the invention allows by the example, sandwich-like intermediate storage of latent storage between two fluid circulation volumes, the latent storage device so that it extends over the entire height of the heat exchanger, ie also over the area provided with heat exchange elements, such as in 5 and 6 is shown. At the in 5 illustrated embodiment forms the latent storage device 20 in the lower region or in Luftein- or exit region of a widening, with the reference numeral 24 is indicated in order to increase the latent storage medium volume. Otherwise, the structure is similar to the above-described embodiments, wherein on the right side in turn a rectangular insert structure for the fluid circulation volume is provided, while on the left side of the latent storage device, a fluid circulation volume with a honeycomb or mesh-like Wärmeleit- and / or structure-increasing use 18 is shown.

In 6 It is indicated how with an extension of the latent storage device over the entire height of the assembly can be easily realized by correspondingly in the latent storage device forming sheets at the level of the collector unit 40 the recirculation of the fluid circulation volume provides corresponding openings, the passage openings for the fluid in the evaporator plates 11 , indicated by the reference numeral 49 , essentially correspond to the passages at the reference numeral 29 indicated in the plates, which define the latent storage volume between them.

In 7 is still indicated, as with a structure in the fluid circulation volume at the reference numeral 19 the U-shaped desired fluid circulation can be achieved by using the respective walls of the reinforcing and / or heat conducting structures to define sub-volumes.

In 8th Finally, various configuration options for an evaporator plate are indicated, namely on the one hand with so-called dimples at the reference numeral 16 or with an insert structure as in the reference numeral 17 indicated. The configuration accordingly corresponds to the reference numeral 17 eg the inserts 12 . 14 . 18 while the indicated deformations with the reference numeral 16 essentially satisfy a configuration as shown on the left side of the latent heat storage in 3 is indicated.

Even though the present invention has been fully described above with reference to the present preferred embodiments described, the skilled artisan should recognize that various changes and modifications are possible within the scope of the claims. In particular, should those skilled in the art will recognize that the latent storage device is also such may be formed that they do not have the entire depth of the heat exchanger extends around e.g. improve the airflow dynamics to be able to since it is particularly easy in this case, the upstream side Behavior of the heat exchanger to optimize, with or without the additional use of fillets or rejuvenating Sections. Furthermore, the person skilled in the art should recognize that the most diverse Features related to a specific embodiment described arbitrarily with features of other embodiments can be combined. It is essential that at least the the transition between the fluid circulation volume and the latent storage area is increased, preferably also the corresponding air passage area between the fluid circulation volume should be increased so that a larger volume for the heat exchange elements in From ribs or fins in heat exchangers at the same volume can be accommodated.

Claims (10)

Heat exchanger having a plurality of tubes provided for heat exchange fluid circulation ( 10 ) given effective heat exchange surface, at least one latent storage device ( 20 ) with given effective heat exchange surface and heat exchange elements ( 30 ), characterized in that the effective heat exchange surface of the latent storage device ( 20 ) to more than 50% effective heat exchange area of heat exchange fluid circulation tubes ( 10 ) adjoins. Heat exchanger according to claim 1, characterized in that the pipes provided for the circulation of heat exchange fluid ( 10 ) Are flat tubes, each with one of its major surfaces to the latent storage device ( 20 ). Heat exchanger according to claim 1 or 2, characterized in that the pipes provided for the circulation of heat exchanger fluid ( 10 ) Are flat tubes, in which the latent storage device 20 is arranged, in particular substantially centrally in it. Heat exchanger according to claim 1, 2 or 3, characterized in that between the heat exchanger fluid and latent storage medium a wall ( 21 . 26 . 28 ) is provided, which with reduced material thickness with respect to a respective opposite wall ( 11 ) provided for the heat exchanger fluid circulation tubes ( 10 ) is present. Heat exchanger according to one of claims 1 to 4, characterized in that between the heat exchanger fluid and latent storage medium a double wall ( 21 . 11 ) is provided, which is formed of substantially plane-parallel sheets. Heat exchanger according to one of claims 1 to 5, characterized in that the pipes provided for the heat exchanger fluid circulation ( 10 ) and / or the latent storage device ( 20 ) inner Wärmeleit- and / or structural elements ( 12 . 14 . 16 . 18 ). Heat exchanger according to one of claims 1 to 6, characterized in that the latent storage device ( 20 ) extends substantially over the entire height of the heat exchanger, in particular to form a widening ( 24 ), especially at the level of a collector ( 40 ) provided for the heat exchanger fluid circulation tubes ( 10 ). Heat exchanger according to one of claims 1 to 7, characterized in that the latent storage device ( 20 ) extends only over a part of the heat exchanger depth, in particular the inflow-side part thereof. Heat exchanger according to one of claims 1 to 8, characterized in that the pipes provided for the heat exchanger fluid circulation ( 10 ) and / or the latent storage device ( 20 ) are formed on the upstream side of the heat exchanger tapered and / or rounded. heat exchangers according to one of the claims 1 to 9, characterized in that it is the fluid side as an evaporator is formed and that the storage material of the latent storage device has a solidus temperature of 3 to 5K.